Adhesive tape



p ,'195s J. N. MASON "$830,003

ADHESIVE TAPE Fil ed Nov. 25, 1955 IN V EN TOR. James N. Mason 2,330,003 ADHESIVE TAPE .lames N. Mason, Winchester, Mass., assignor, by'mesne assignments, to American Biltrite Rubber Company, Inc, a corporation of Delaware Application November 25, 1955, Serial No. 549,017 6 Claims. (Cl. 154-121) The present invention relates to pressure sensitive adhesive tape and to a novel method of making it, and is more particularly concerned with tapes comprising a fabric backing web and a pressure-sensitive adhesive coating on one or both sides of the fabric.

Tapes of this'type are typically used in electricwiring work to protect or cover an electric conductor, about which the tape is wound either directly or over a preliminary winding of insulation. 'To give satisfactory service the tape should provide a strong impervious and durable covering for the conductor.

Since in practically all applications employing adhesive tape of this type the tape is manually wound to the conductor, generally directly from the roll, and is then torn from the roll, the resistance of the tape to tearing should not be excessive. The tape should, however, have a substantial fabric backing of considerable wear resistance to adequately serve its purpose, and inaddition should be of substantial and uniform thickness to permit easy handling and a uniform product.

An ideal fabric for tapes should accordingly possess the rather inconsistent properties of substantial uniform thickness, adequate tensile strength and wearing properties and be in addition, readily torn. Numerous means for providing these characteristics have been proposed, most all of them having serious drawbacks. For instance, warp threads of low strength may be used, but such are of small diameter and thus not only result in a tape of reduced thickness but also in a non-uniform weave which frequently leads to the formation of open spaces or pinholes? in the finished product. Another way of reducing the tear resistance is to use a fabric that has been treated with a filler to stifien it such that upon tearing the normal elongation of the warp threads is prevented. The tearing stresses are thus applied to the warp threads in a one at a time sequence, and the fabric is more easily .torn. The stiffness of the fabric, however, is generally undesirable since it makes the tape diflicult to handle.

The principal object of the present invention is to provide easily tearable fabric backed pressure-sensitive adhesive tape in which the disadvantages of the prior tapes are avoided. The invention consists in first treating a cotton backing fabric with a solution of a reagent which is reactive with cellulose to cause chemical degradation and weakening of the fabric, such that between about 75 and 90% of the original tensile strength is retained.

Numerous reagents will react with cotton to cause degradation of the cellulose and weakening of the fabric, such as acids, andoxidizing agents, all of which cause cleavage or other degradation of the cellulose molecules. The conditions of treatment may vary according to the particular reagent, and those such as concentration, time, and temperature are inter-dependent in accocrdance with well-known concepts of chemical kinetics. In any case, the treatment will be carried out to the extent that the fabric loses between about and 25% of its original tensile strength. The fabric is then washed of excess reagent, and dried.

Cotton fabric so treated is admirably suited for. use

in the manufacture of pressure sensitive adhesive tape,

which may typically be carried out by applying a layer of pressure sensitive material to one, or if desired to both, sides of the fabric, conveniently by calender'ing the material onto the fabric. The coated fabric is then rolled, preferably with an interleaving sheet of a liner,

- e. g. waxed or lacquered paper, and then cut into separate rolls of tape which are ready for their customary use.

This invention will be better understood and appreciated from the following detailed description of a preferred embodiment selected for purposes of illustration and shown in the accompanying drawings in which:

Fig. 1' is adiagr-ammatic illustration of'a continuous process for treating fabric in accordance with this invention,

Fig. 2 diagrammatically illustrates. the application of pressure sensitive adhesive tapes to the fabric,

Fig. 3 shows schematically the cutting of the rolled coated fabric into individual rolls of tape, and

Fig. 4 is a perspective view of the finished stack of tape rolls.

The first step in carrying out the invention, as shown schematically in Fig. 1, consists in treating the fabric 10, such as an unbleachedcotton muslin having an initial tensile strength warpwise of 52lbs. per lineal inch, by

feeding it from a roll 12 through a bath 14 of the treat ing solution in which the fabric'passes up and down around feed rollers 16. The rollers 16 are so arranged as to hold the fabric in the bath 14 for the time necessary under the conditions of treatment to bring about the desired loss in strength.

Typically, the treating solution consists of an aqueous solution of sodium hypochlorite of concentration giving 0.3% by weight of free available chlorine. At a temperature of 140 F. the fabric should remain in the solution for about minutes.

When the fabric emerges from the bath 14 it is passed through a rinsing tank 18 fed with fresh water to remove excess reagent, and is then passed through a drier 20 and the dried treated fabric is collected on a roll 22.

Application of a pressure sensitive adhesive coating, as suggested by Fig. 2, is conveniently accomplished by feeding the treated fabric from the roll 22 through a calender coating machine 24 which applies a layer of the pressure sensitive adhesive material 26' to a surface of the fabric 10. Typically, the calender coating machine consists of three rollers 27, 28 and 29 driven together in well-known fashion. The adhesive material 26 is.

retained as a reservoir between the upper and center rollers 27 and 28, which are so spaced apart that the required amount is carriedaround by the center roller 28. The fabric 10' is fed between 1 the center roller 28 and the lower roller 29, and picks up the layer of adhesive material from the center roller. After leaving the calender coating machine 24, the fabric is wound into a roll 30, preferably together with a liner sheet 31 of, for instance, waxed paper interleaved with the coated fabric to prevent blocking.

Tape is formed from the coated sheet as shown in Fig. 3 by feeding it from the roll 30 over an arbor 32 against which run several spaced knife disks'34 cutting the sheet into strips. The strips are wound simultaneously onto a mandrel 36 as a plurality of tape rolls 38,

which may be separated when the mandrel is removed as suggested by Fig. 4.

The pressure-sensitive adhesive material may be any of a number of well-known compositions, and its precise formulation forms. no part of this invention.

Naturalcrepe rubber -75 V fatented Apr. 8, 1 958 I One preferred formula for insulating tape is made up as follows:

Parts by weight 7 2,sao,ooa

a pasty consistency suitable for application by means of the calender. 7

Other, treatments whichimay. also be used-to weaken the fabricbackiug material consist in immersing the fabric in aqueousacidici solutions, which have the effect of causing degradation of the cellulose. Any of the strong mineral acidsas well as strong organic acids may be used, such as sulfuric acid, hydrochloric acid, nitricacid, acetic acid, to name but a few. In atypical acid treatment using'sulfuric acid, satisfactory weakening may be attained, by immersing the fabric solutionat 145? F. for 45 minutes; Similar resultsmay be achieved with stronger solutions, e. g. a sulfuric acid solution at 120 F. for minutes. Stronger solutions do, however, react more rapidly and the time of immersion then. becomes increasingly. critical.

.The foregoing exampleshave been given as illustrative of this invention and not by way of implying limitation to the invention. It is rather contemplated that obvious modifications will occur to those skilledin the art, and that such may be made. without departing from. the scope of this invention. I V t Having thus disclosed-my inventionv and described in detail preferred embodiments thereof, I claim and desire to secure by LettersPatent:

1. The process of making easily tearable woven fabricbacked pressure sensitive adhesive tape comprising passing a web of woven cellulosic fabric through a treating bath of a treating solution comprising a reagent reactive with cellulose to cause degradation and weakening of the fabric and maintaining said solution in contact with saidfabric until the tensile strength of said fabric has been reduced by from about 10 to percent of its original tensile strength, whereby a fabric of the desired dimensions but of greatly reduced strength is produced, rinsing and drying the fabric, applyinga surface layer of a pressure-sensitive adhesive composition to the fabric, winding the fabric with a liner web into. a roll and cutting the fabric roll into separate rolls of tape.

2. The process of making easily tearable woven fabricbacked pressure sensitive adhesive tape comprising passing a web of woven cellulosic fabric through a treating. bath of a treating solution comprising areagent reactive with cellulose to cause degradation and weakening of the fabric and maintaining said solution in contact with said fabric until the tensile strength of said fabric has been reduced by from 10 to 25 percent of its original tensile strength, whereby a fabric of the desired dimensions but of greatly reduced strength is produced, rinsing and drying the fabric, and applying'a surface layer'of a pressure-sensitive adhesive composition to the fabric.

3; In the process of making easily tearable fabric-backed pressure, sensitive adhesive tape wherein a surface coating is applied to a cellulosic fabric backing, the improvein a 0.8% sulfuric acid' ment comprising passing the fabric through an aqueous solution of a reagent reactive with cellulose to cause degradation and weakening of the fabric to reduce the tensile strength of said fabric by from 10-25% of its original tensile strength.

4. The: process of making easily tearable woven fabricbacked pressure sensitive adhesive tape comprising passing a web of woven cellulosic fabric through a treating bath of a treating solution comprising an oxidizing agent reactive with cellulose to cause degradation and weakening of the fabric and maintaining said solution in contact with said fabric until the tensile strength of said fabric has been reduced byfrom about 10 to 25 percent of its original tensilestrength, whereby a fabric of the desired dimensions but of greatly reduced strength is produced, rinsing and drying the fabric, and applying a surface layer of a pressure-sensitive adhesive composition to the fabric.

5. The method defined by claim 4 wherein the treating solution of an oxidizing agent is an aqueous hypochlorite solution containing about 0.3% of available chlorine having a temperature of about F., and the time of the treatment is about 45, minutes.

6. The method. defined by claim 2 wherein the solution is an aqueous solution of a sulfuric acid of concentration between 0.8 and 5% at a temperature between about 120 F. and R, and the time of treatment is between about 20 and 45 minutes, said treatment being effective to reduce the tensile strength of the fabric by between 10 and 25% of itsoriginal tensile strength.

References Cited in the file of this patent UNITED STATES PATENTS 1,465,093 Respess Aug. 14, 1923 1,503,337 Seiglev July 29, 1924 1,769,611 Warp July 1, 1930 1,781,896 Diamond Nov. 18, 1930 2,241,384 Bateman et a1. May 13, 1941 2,508,855 Brown May 23, .1950

OTHER REFERENCES Matthews: Bleaching and Related Processes, The Chemical Catalog Company, Inc., New York, N. Y. (1921), pp. 331-335. 7

Matthews: Bleaching and Related Processes, pp. 477-479, The Chemical Catalog Co., Inc., New York, N. Y. (1921). 

1. THE PROCESS OF MAKING EASILY TEARABLE WOVEN FABRICBACKED PRESSURE SENSITIVE ADHESIVE TAPE COMPRISING PASSING A WEB OF WOVEN CELLULOSIC FABRIC THROUGH A TREATING BATH OF A TREATING SOLUTION COMPRISING A REAGENT REACTIVE WITH CELLULOSE TO CAUSE DEGRADATION AND WEAKENING OF THE FABRIC AND MAINTAINING SAID SOLUTION IN CONTACT WITH SAID FABRIC UNTIL THE TENSILE STRENGTH OF SAID FABRIC HAS BEEN REDUCED BY FROM ABOUT 10 TO 25 PERCENT OF ITS ORIGINAL TENSILE STRENGTH, WHEREBY A FABRIC OF THE DESIRED DIMENSIONS BUT OF GREATLY REDUCED STRENGTH IS PRODUCED, RINSING AND DRYING THE FABRIC, APPLYING A SURFACE LAYER OF A PRESSURE-SENSITIVE ADHESIVE COMPOSITION TO THE FABRIC, WINDING THE FABRIC WITH A LINER WEB INTO A ROLL AND CUTTING THE FABRIC ROLL INTO SEPARATE ROLLS OF TAPE. 